a 1.5 to a 1.8 is a PITA
it can be done... I believe bruce95fmla has done it, but I do recall him saying it was an ordeal. the 1.5 is a lot of fun. I had one and I totally miss it. its a good "beater" I guess you can say, but it is fun and it can hold its own in auto-X.
as for the other swaps...